Pass data from Application to the Activity

Question

My android Application class instance is listening to the third-party service for the event. Then the event is coming out, I need to notice my Activity about it. What is the right way to do that? I know about startActivity() method, but my Activity is running yet!

Answer 1

If the communication is local to your app you can use local broadcasts.

For communication between components you can also use EventBus (Android-library). It is really easy to use and implement (takes less than a minute to understand how it works) and is great in performance.

Answer 2

Use Local broadcast events with LocalBroadcastManager - see this tutorial for more information.

I have copied relevant bits of code from the above tutorial for your convenience.

To notify your already running activity about your event, try the following:

1. Send a broadcast intent from your Application class when you receive the event.

   Intent intent = new Intent("my-event");
   // add data
   intent.putExtra("message", "data");
   LocalBroadcastManager.getInstance(this).sendBroadcast(intent);
   

2. Register a BroadcastReceiver in your Activity which will handle the received Intents for your event. Add the following code to your Activity:

   @Override 
   public void onResume() {
     super.onResume();
   
     // Register mMessageReceiver to receive messages.
     LocalBroadcastManager.getInstance(this).registerReceiver(mMessageReceiver,
     new IntentFilter("my-event"));
   }
   
   // handler for received Intents for the "my-event" event 
   private BroadcastReceiver mMessageReceiver = new BroadcastReceiver() {
     @Override
     public void onReceive(Context context, Intent intent) {
       // Extract data included in the Intent
       String message = intent.getStringExtra("message");
       Log.d("receiver", "Got message: " + message);
     }
   };
   
   @Override
   protected void onPause() {
     // Unregister since the activity is not visible
     LocalBroadcastManager.getInstance(this).unregisterReceiver(mMessageReceiver);
     super.onPause();
   }